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Register a new userMagnetic field induced quantum spin liquid in the two coupled trillium lattices of K$_2$Ni$_2$(SO$_4$)$_3$
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Ivica \\v{Z}ivkovi\\'c Dr
Publication date
2021
fields
Physics
and research's language is
English
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Quantum spin liquids are exotic states of matter which form when strongly frustrated magnetic interactions induce a highly entangled quantum paramagnet far below the energy scale of the magnetic interactions. Three-dimensional cases are especially challenging due to the significant reduction of the influence of quantum fluctuations. Here, we report the magnetic characterization of {kni} forming a three dimensional network of Ni$^{2+}$ spins. Using density functional theory calculations we show that this network consists of two interconnected spin-1 trillium lattices. In the absence of a magnetic field, magnetization, specific heat, neutron scattering and muon spin relaxation experiments demonstrate a highly correlated and dynamic state, coexisting with a peculiar, very small static component exhibiting a strongly renormalized moment. A magnetic field $B gtrsim 4$ T diminishes the ordered component and drives the system in a pure quantum spin liquid state. This shows that a system of interconnected $S=1$ trillium lattices exhibit a significantly elevated level of geometrical frustration.
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Two-dimensional triangular-lattice materials with spin-1/2 are perfect platforms for investigating quantum frustrated physics with spin fluctuations. Here we report the structure, magnetization, heat capacity and inelastic neutron scattering (INS) results on cesium ytterbium diselenide, CsYbSe$_2$. There is no long-range magnetic order down to 0.4 K at zero field. The temperature dependent magnetization, $M(T)$, reveals an easy-plane magnetic anisotropy. A maximum is found in $M(T)$ around emph{T}$sim$1.5 K when magnetic field $H$ is applied in the $ab$ plane, indicating the short-range interaction. The low-temperature isothermal magnetization $M(H)$ shows a one-third plateau of the estimated saturation moment, that is characteristic of a two-dimensional frustrated triangular lattice. Heat capacity shows field-induced long-range magnetic order for both $H||c$ and $H||ab$ directions. The broad peak in heat capacity and highly damped INS magnetic excitation at $T$=2 K suggests strong spin fluctuations. The dispersive in-plane INS, centered at the (1/3 1/3 0) point, and the absence of dispersion along $c$ direction suggests 120$^{circ}$ non-collinear 2D-like spin correlations. All these results indicate that the two-dimensional frustrated material CsYbSe$_2$ can be in proximity to the triangular-lattice quantum spin liquid. We propose an experimental low-temperature $H$-$T$ phase diagram for CsYbSe$_2$.
K$_3$Cu$_3$AlO$_2$(SO$_4$)$_4$ is a highly one-dimensional spin-1/2 inequilateral diamond-chain antiferromagnet. Spinon continuum and spin-singlet dimer excitations are observed in the inelastic neutron scattering spectra, which is in excellent agreement with a theoretical prediction: a dimer-monomer composite structure, where the dimer is caused by strong antiferromagnetic (AFM) coupling and the monomer forms an almost isolated quantum AFM chain controlling low-energy excitations. Moreover, muon spin rotation/relaxation spectroscopy shows no long-range ordering down to 90~mK, which is roughly three orders of magnitude lower than the exchange interaction of the quantum AFM chain. K$_3$Cu$_3$AlO$_2$(SO$_4$)$_4$ is, thus, regarded as a compound that exhibits a Tomonaga-Luttinger spin liquid behavior at low temperatures close to the ground state.
Kitaev quantum spin liquids (QSLs) are exotic states of matter that are predicted to host Majorana fermions and gauge flux excitations. However, so far all known Kitaev QSL candidates are known to have appreciable non-Kitaev interactions that pushes these systems far from the QSL regime. Using time-domain terahertz spectroscopy (TDTS) we show that the honeycomb cobalt-based Kitaev QSL candidate, BaCo$_2$(AsO$_4$)$_2$, has dominant Kitaev interactions. Due to only small non-Kitaev terms a magnetic continuum consistent with Majorana fermions and the existence of a Kitaev QSL can be induced by a small 4 T out-of-plane-magnetic field. Applying an even smaller in-plane magnetic field $sim$ 0.5 T suppresses the effects of the non-Kitaev interactions and gives rise to a field induced intermediate state also consistent with a QSL. These results may have fundamental impact for realizing quantum computation. Our results demonstrate BaCo$_2$(AsO$_4$)$_2$ as a far more ideal version of Kitaev QSL compared with other candidates.
$Ni Cl_2$-$4SC(NH_2)_2$ (known as DTN) is a spin-1 material with a strong single-ion anisotropy that is regarded as a new candidate for Bose-Einstein condensation (BEC) of spin degrees of freedom. We present a systematic study of the low-energy excitation spectrum of DTN in the field-induced magnetically ordered phase by means of high-field electron spin resonance measurements at temperatures down to 0.45 K. We argue that two gapped modes observed in the experiment can be consistently interpreted within a four-sublattice antiferromagnet model with a finite interaction between two tetragonal subsystems and unbroken axial symmetry. The latter is crucial for the interpretation of the field-induced ordering in DTN in terms of BEC.
The bulk single crystals of $S = 1$ chain compound Ni(C$_3$H$_{10}$N$_2$)$_2$NO$_2$ClO$_4$ are grown by using a slow evaporation method at a constant temperature and a slow cooling method. It is found that the optimum condition of growing large crystals is via slow evaporation at 25 $^circ$C using 0.015 mol Ni(ClO$_4$)$_2$$cdot$6H$_2$O, 0.015 mol NaNO$_2$, and 0.03 mol 1,3-propanediamine liquid dissolved into 30 ml aqueous solvent. High-quality crystals with size up to $18 times 7.5 times 5$ mm$^3$ are obtained. The single crystals are characterized by measurements of x-ray diffraction, magnetic susceptibility, specific heat and thermal conductivity. The susceptibilities along three crystallographic axes are found to exhibit broad peaks at $sim 55$ K, and then decrease abruptly to zero at lower temperatures, which is characteristic of a Haldane chain system. The specific heat and the thermal conductivity along the $c$ axis can be attributed to the simple phononic contribution and are analyzed using the Debye approximation.
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